One hundred and thirty nine volunteers were screened for the study, 33 were found not eligible based on the inclusion and exclusion criteria, 18 cancelled their appointments before screening, 88 were consented and completed all procedures of the study. Eleven of the 88 volunteers were accrued since last review. Enrollment is dependent on the type of patients enrolled in other NINR protocols requiring age-, gender-, race-matched controls. Recruitment conducted by self-referral or by referrals from the Clinical Research Volunteer Program of the Patient Recruitment and Public Liaison Office.